The present invention relates to novel 1,5 and 3,6-substituted indole compounds having nitric oxide synthase (NOS) inhibitory activity, to pharmaceutical and diagnostic compositions containing them, and to their medical use, particularly as compounds for the treatment of stroke, reperfusion injury, neurodegenerative disorders, head trauma, coronary artery bypass graft (CABG) associated neurological damage, migraine with and without aura, migraine with allodynia, chronic tension type headache (CTTH), neuropathic pain, central post-stroke pain (CPSP), and chronic pain.
Nitric oxide (NO) has diverse roles both in normal and pathological processes, including the regulation of blood pressure, in neurotransmission, and in the macrophage defense systems (Snyder et al., Scientific American, May 1992:68). NO is synthesized by three isoforms of nitric oxide synthase, a constitutive form in endothelial cells (eNOS), a constitutive form in neuronal cells (nNOS), and an inducible form found in macrophage cells (iNOS). These enzymes are homodimeric proteins that catalyze a five-electron oxidation of L-arginine, yielding NO and citrulline. The role of NO produced by each of the NOS isoforms is quite unique. Overstimulation or overproduction of individual NOS isoforms especially nNOS and iNOS, plays a role in several disorders, including septic shock, arthritis, diabetes, ischemia-reperfusion injury, pain, and various neurodegenerative diseases (Kerwin, et al., J. Med. Chem. 38:4343, 1995), while eNOS inhibition leads to unwanted effects such as enhanced white cell and platelet activation, hypertension and increased atherogenesis (Valance and Leiper, Nature Rev. Drug Disc. 2002, 1, 939).
NOS inhibitors have the potential to be used as therapeutic agents in many disorders. However, the preservation of physiologically important nitric oxide synthase function suggests the desirability of the development of isoform-selective inhibitors that preferentially inhibit nNOS over eNOS.